If you want to encrypt your secrets for multiple recipients you will need a GPG key. We tend to follow the advice of Debian when creating new keys and as such:

You should go for a 4096 bit key

You should avoid SHA1 as your preferred hash

You can generate a signing and encryption key has follows:

paul@jolt:~$ gpg --gen-key
gpg (GnuPG) 1.4.10; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
gpg: directory `/home/paul/.gnupg' created
gpg: new configuration file `/home/paul/.gnupg/gpg.conf' created
gpg: WARNING: options in `/home/paul/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/home/paul/.gnupg/secring.gpg' created
gpg: keyring `/home/paul/.gnupg/pubring.gpg' created
Please select what kind of key you want:
(1) RSA and RSA (default)
(2) DSA and Elgamal
(3) DSA (sign only)
(4) RSA (sign only)
Your selection? 1
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 4096
Requested keysize is 4096 bits
Please specify how long the key should be valid.
0 = key does not expire
<n> = key expires in n days
<n>w = key expires in n weeks
<n>m = key expires in n months
<n>y = key expires in n years
Key is valid for? (0) 0
Key does not expire at all
Is this correct? (y/N) y
You need a user ID to identify your key; the software constructs the user ID
from the Real Name, Comment and E-mail Address in this form:
"Heinrich Heine (Der Dichter) <heinrichh@duesseldorf.de>"
Real name: Paul Ubbot
E-mail address: pubbot@example.com
Comment:
You selected this USER-ID:
"Paul Ubbot <pubbot@example.com>"
Change (N)ame, (C)omment, (E)-mail or (O)kay/(Q)uit? O
You need a Passphrase to protect your secret key.
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, use the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
Not enough random bytes available. Please do some other work to give
the OS a chance to collect more entropy! (Need 284 more bytes)
+++++
...............................+++++
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, use the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
......+++++
.......+++++
gpg: /home/paul/.gnupg/trustdb.gpg: trustdb created
gpg: key D770E8A9 marked as ultimately trusted
public and secret key created and signed.
gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u
pub 4096R/D770E8A9 2013-08-28
Key fingerprint = 746B 2477 FB6F CCC6 46C2 D5D2 288C EF6D D770 E8A9
uid Paul Ubbot <pubbot@example.com>
sub 4096R/49BEE9E3 2013-08-28

You now have a GPG key.

Ideally you should sign the keys of the people you are working with to build a web of trust, however there is no requirement to do so. There are excellent resources online for holding a key signing event.

In order to encrypt for you collaborators will need a copy of the public portion of your key. You can publish your key like so:

It will transparently decrypt the file, allow you to edit the text contents, then when you save it will re-encrypt it. It will preserve the same recipients, which is very useful if you are working with a team.